Propolis extract combined with oregano essential oil applied to lima bean seeds against Sclerotinia sclerotiorum

European Journal of Plant Pathology - In this study, propolis extract (EPE) and oregano essential oil (OEO), both natural products with different bioactive compounds, were evaluated in vitro and in...     

Correction to: Propolis extract combined with oregano essential oil applied to lima bean seeds against Sclerotinia sclerotiorum

European Journal of Plant Pathology - Volatile fatty acids (VFAs) play a role in suppression of plant pathogens during anaerobic soil disinfestation (ASD), but it is unclear how VFAs in anaerobic...     

Induced resistance against Sclerotinia sclerotiorum in kiwifruit leaves

Salicylic acid (SA), 1-aminocyclopropane-1-carboxylic acid (ACC) and DL -β-amino- n -butyric acid (BABA) were screened for the ability to induce phenylalanine ammonia lyase (PAL) activity in kiwifruit ( Actinidia deliciosa 'Hayward') leaves. SA (2 m M ) was the most effective and induced a 10-fold rise in PAL activity after 2 days compared with a four-fold rise 5 days after ACC (0.5 m M ) treatment. BABA was not an effective elicitor of PAL. SA was further tested, alongside a chlorinated analogue 4-chlorosalicylic acid (4CSA), for the ability to control Sclerotinia sclerotiorum on kiwifruit leaves. Pretreatment with SA and 4CSA caused a reduction in the size of lesions arising from subsequent S. sclerotiorum infection. 4CSA was the more effective and reduced disease levels, relative to controls, by up to 85% on leaf discs and 78% on leaves on the vine. This compares with a 48% reduction by SA on both. Resistance to infection was not affected by washing treated leaf discs prior to inoculation or by delaying inoculation for up to 4 days following 4CSA application. SA and 4CSA were rapidly absorbed and metabolized by kiwifruit leaves and had no apparent phytotoxic effects at the concentrations used for disease control studies. It is proposed that SA and 4CSA operate through the induction of host resistance mechanisms.     

Molecular,morphological and pathogenic diversity of Sclerotinia sclerotiorum isolates from common bean (Phaseolus vulgaris) fields in Argentina

White mould, caused by Sclerotinia sclerotiorum, is one of the most threatening fungal diseases occurring across major bean production regions worldwide. In Argentina, under favourable weather conditions, up to 100% seed yield losses occur on susceptible common bean cultivars. The aim of this study was to characterize the diversity of S. sclerotiorum isolates from six dry bean fields in the main production area of Argentina by means of molecular, morphological (mycelium colour, number and pattern of sclerotia distribution) and pathogenic approaches. Among 116 isolates analysed, high genotypic and morphological variability was observed. A total of 52 mycelial compatibility groups (MCGs) and 59 URPs (universal rice primers) molecular haplotypes were found. All the MCGs were location specific, while only 12% of the URP haplotypes were shared among locations. The molecular analysis of variance revealed a significant differentiation among populations, with higher genetic variability within the populations analysed than among them. The aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. Most of the isolates were highly aggressive, while no variation among locations was observed. The information generated in the present study provides, for the first time, information on the variability of S. sclerotiorum associated with white mould in the main common bean production area in Argentina. In addition, the findings suggest the occurrence of both clonal and sexual reproduction in the populations analysed. This work contributes to the development of sustainable management strategies in bean production aimed to minimize yield losses due to white mould.     

拮抗核盘菌Bt菌株的筛选及抑菌活性研究

利用平板对峙试验从170株Bt菌株中筛选获得12株对核盘菌Sclerotinia sclerotiorum有抑菌活性的菌株,对其中4株活性较强的菌株进行抗病相关基因分析,发现菌株中都含有几丁质酶基因,测定4AP1菌株发酵液的几丁质酶活力为672.4U/mL。通过对4AP1菌株pH和温度敏感性的研究发现,4AP1菌株最高可耐受55℃高温及pH 12缓冲液的处理,抑菌活性与对照无显著差异。且该菌株抑菌谱较广,除核盘菌外,对小麦赤霉病菌Fusarium graminearum等其他9种病原真菌均有抑制作用。本研究获得的4AP1菌株对核盘菌具有较强抑制作用,且耐热耐强碱环境,为构建杀虫抗病Bt工程菌提供了菌株资源。     

盾壳霉对核盘菌的拮抗作用研究

系统研究了菌核重寄生菌盾壳霉对核盘菌的拮抗作用,结果表明:盾壳霉可在核盘菌菌落上寄生,使核盘菌菌丝消解、原生质泄露,并抑制菌核的形成;而且盾壳霉提前6d接种,其分泌的抗生物质还可抑制核盘菌菌丝生长,并产生明显抑菌带。盾壳霉孢子液喷雾处理也证明:盾壳霉分生孢子即可在核盘菌子囊盘(柄)上萌发、寄生,使子囊盘(柄)萎缩枯死,而且还可以在核盘菌菌落上萌发、寄生,消解破坏菌丝体、抑制的菌核形成。     

Phytoalexin accumulation during infection of bean and soybean by ascospores and mycelium of Sclerotinia sclerotiorum

Infection by ascospores of Sclerotinia selerotiorum caused hypersensitivity in epidermal cells in leaves and etiolated hypocotyls of bean and soybean. In bean, phaseollin and phaseollidin accumulated in leaves but kievitone alone in hypocotyls. In soybean, no phytoalexins were detected in leaves but glyceollin accumulated in hypocotyls.
Mycelial infection caused water-soaked spreading lesions in leaves and etiolated hypocotyls of both hosts. In bean, no phytoalexins were detected in leaves but kievitone alone accumulated in hypocotyls. In soybean, glyceollin accumulated in leaves but was not sought in hypocotyls.
Transfer of bean hypocotyls infected with mycelium from 18 to 28°C caused lesion limitation and marked accumulation of phaseollin and kievitone.
Phaseollin, kievitone and glyceollin inhibited ascospore germination and growth of hyphae from preformed germ-tubes and established mycelia, phaseollin being most active and glyceollin least active. Hyphal growth from mycelia was least affected by the phytoalexins.     

Effect of E-cinnamaldehyde against Sclerotinia sclerotiorum on potato and induction of glutathione S-transferase genes

This research was carried out to assess the effect of E-cinnamaldehyde (EC) against Sclerotinia sclerotiorum, causal agent of potato white mold, under invivo and invitro conditions. Based on the results, EC was able to completely inhibit (P < 0.05) mycelial growth of four isolates in both volatile and contact phases after five days of inoculation at the concentrations 500 μl and 5 μl/ml, respectively. Moreover EC at concentrations 30 and 50 μl EC/ml sterile distilled water significantly reduced white mold on six potato cultivars including Pashandi, Istambouli, Agria, Marfauna, Alpha and Spartaan in greenhouse trials. In next step, induction of glutathione S-transferase (GST)-like genes identified from the pathogen (isolate 3) genome was assessed. After 2 h of exposure to both EC and cinnamom extract, four genes with locus numbers SS1G_07319.1, SS1G_07195.1, SS1G_00703.1 and SS1G_01918.1 were up-regulated. Furthermore, EC and cinnamon extract appeared to have no effect on gene expression in SS1G_10295.1. In this study, enzyme activity of GST was determined with 1-chloro-2, 4-dinitrobenzene as substrate. While enzymatic activity was 42.3 and 45.6 units mg⁻¹ protein in sterilized distilled water and ethyl acetate, respectively, it was recorded as 78.9 and 86.4 units mg⁻¹ protein for cinnamon extract and EC, respectively.     

Screening resistance against Sclerotinia sclerotiorum in Brassica crops with use of detached stem assay under controlled environment

Sclerotinia sclerotiorum is a major pathogen that infects stem tissue, causing yield loss and poor seed quality in rapeseed (Brassica napus). Here we report a reliable detached stem inoculation method for evaluating resistance under controlled environment. Two sets of Brassica materials were employed, including 17 genotypes from five Brassica crops in experiment 1, and 71 F₂ lines derived from a cross between susceptible and resistant lines of B. oleracea in experiment 2. High correlations were detected between stem and branch for lesion length in both experiments and between stem and sections of stem in experiment 1. Although the lesion length of detached stem inoculation under controlled environment was positively correlated with that of toothpick inoculation in the field, the variation of lesion length in the detached stem inoculation was lower than that in toothpick inoculation in experiment 2. Moreover, no significant association was detected between lesion length and the diameter of stem or branch. These findings suggest that the detached stem inoculation under controlled conditions is a large-scale, flexible and reliable method of screening for resistance against S. sclerotiorum in Brassica crops. The application of detached stem inoculation is discussed in resistance breeding programs against S. sclerotiorum in Brassica crops.     

In vitro and in vivo antifungal activity of synthetic pure isothiocyanates against Sclerotinia sclerotiorum

BACKGROUND: Isothiocyanates (ITCs) released by the enzymatic hydrolysis of glucosinolates in the Brassicaceae are potentially useful for controlling fungal pathogens. In vitro activity of pure ITCs against Sclerotinia sclerotiorum (Lib.) de Bary was studied by adding them to glass filters in petri dishes and dissolving them in the growing media. RESULTS: Methyl, allyl and benzyl ITCs were the most fungitoxic of the compounds in bioassays with S. sclerotiorum isolate Ss31. In the volatile phase, mycelial growth was completely inhibited by these three compounds. Aromatic ITCs were less toxic in the petri dishes but were more toxic than aliphatic ITCs when dissolved in the agar. Benzyl ITC exhibited the highest inhibitory effect on sclerotial germination, with an EC₅₀ value of 75.1 µmol L^?1. Butyl and benzyl ITCs reduced apothecial production of S. sclerotiorum by 92.5% at the highest concentration. In in vivo assay, only allyl and 2‐phenylethyl ITCs reduced disease incidence (by 76.7 and 70% respectively) at low concentrations. CONCLUSION: Sclerotinia sclerotiorum in the soil might be suppressed by the higher concentrations of allyl and benzyl ITCs released from decomposition of Brassica juncea, B. carinata, B. nigra and Sinapis spp. Copyright © 2011 Society of Chemical Industry     

核盘菌一分支酸变位酶同源效应蛋白的亚细胞定位

前期研究表明核盘菌Sclerotinia sclerotiorum产生的一种分支酸变位酶同源效应蛋白能够提高其致病能力。为了进一步研究该效应蛋白在核盘菌致病过程中的作用机制,我们通过构建GFP融合蛋白对其分泌行为和亚细胞定位开展了研究。首先通过PCR技术扩增了该基因的启动区+信号肽(SP)+叶绿体定位肽(CTP)的DNA序列,构建GFP融合载体,然后借助REMI技术转化核盘菌原生质体,筛选GFP能够表达的转化子,最后接种转化子菌丝于烟草叶片,激光共聚焦检测GFP荧光信号,发现GFP荧光与叶绿体自体荧光共定位,表明该效应蛋白可分泌进入寄主叶绿体内发挥作用。     

Low genetic variability in Sclerotinia sclerotiorum populations from common bean fields in Minas Gerais State,Brazil, at regional,local and micro‐scales

Sclerotinia sclerotiorum, causal agent of white mould, is the most destructive and widely distributed soilborne pathogen of common bean during the autumn–winter season in Brazil. Nevertheless, little is known about the genetic structure of the pathogen population. Microsatellite (SSR) markers and mycelial compatibility groups (MCGs) were used to characterize 118 isolates collected from 20 bean fields located in the most important growing regions of Minas Gerais State (MG). Additionally, the genetic variability among 10 isolates obtained from a single sclerotium was investigated in 10 different sclerotia. Seventy SSR haplotypes and 14 MCGs were identified among the 118 isolates. The genetic differences within bean growing areas accounted for most of the genetic variation (72%). Despite the relatively high genotypic diversity, the SSR loci were at linkage disequilibrium. Moreover, 70% of the isolates were assigned to only two MCGs, and haplotypes of a given MCG were closely related. The discriminant analysis of principal components revealed five groups. There was strong genetic differentiation between isolates collected in one municipality in southern MG when compared to other regions. Common bean resistance to white mould should be assessed with representative isolates of the five genetic groups and, if possible, of the different MCGs detected in the present study. One to five haplotypes were detected among the 10 isolates obtained from a single sclerotium. Therefore, in order to ensure genetic identity of an isolate, hyphal tip or monoascosporic isolates should be used.     

Changes in susceptibility of bean leaves (Phaseolus vulgaris) to Sclerotinia sclerotiorum and Botrytis cinerea by pre-inoculative ozone exposures

The effects of ozone on the susceptibility of leaves ofPhaseolus vulgaris toSclerotinia sclerotiorum andBotrytis cinerea have been investigated. Seedlings of one ozone-sensitive (Pros) and five relatively ozone-insensitive cultivars (Gamin, Precores, Groffy, Narda, Berna) were exposed to different ozone concentrations (0, 120, 180 and 270 g m^–3) for 8 h. One day after the exposures, primary leaves were detached and immediately inoculated with spores of either pathogen suspended in water or in a 62.5 mM KH₂PO₄ (Pi) solution. Visible ozone injury differed between the cultivars and increased with increasing ozone concentration. On the leaves of non-exposed plants, spores of the pathogens suspended in water caused very few lesions, whereas fungal pathogenicity was stimulated by addition of Pi to the inoculum. Ozone-injured leaves of all cultivars exhibited lesions after inoculation of the leaves with the pathogens suspended in water, and the number of lesions was positively correlated with the level of ozone injury for either pathogen and cultivar. The increase in susceptibility of bean leaves in response to increasing ozone concentrations was greater forB. cinerea than forS. sclerotiorum when spores were suspended in water, but was similar when the spores were suspended in Pi.In general, the number of lesions following inoculation with spores in Pi increased with increasing ozone concentration. However, the number of lesions in the ozone-insensitive Groffy was reduced by an exposure to 120 g m^–3 but increased with higher concentrations. This pattern of susceptibility response to the pathogens was not found in the other ozone-insensitive cultivars and, thus, did not appear to be related to the inherent ozone-insensitivity in bean.     

8种杀菌剂对西兰花菌核病的防治效果及对制种产量的影响

本文开展了8种杀菌剂对制种西兰花菌核病的防治效果试验。结果表明8种杀菌剂均有防治效果,以40%菌核净可湿性粉剂的防治效果最好,防效为99.19%,比空白对照增产167.05%,千粒重最高,达到5.38g;其次为2亿活孢子/g木霉菌可湿性粉剂和50%腐霉利可湿性粉剂,防效分别为82.39%和81.69%,比空白对照分别增产147.44%和151.70%,千粒重分别为5.34和5.36g。其他杀菌剂的防治效果为51.06%~73.23%,比对照增产76.99%~107.39%,千粒重为4.73~5.28g,空白对照的千粒重为3.23g。综合分析认为,制种西兰花菌核病的防治可选用40%菌核净可湿性粉剂、2亿活孢子/g木霉菌可湿性粉剂和50%腐霉利可湿性粉剂等3种杀菌剂,并交替轮流使用。     

Biochemical defence responses in primary roots of Scots pine challenged in vitro with Cylindrocarpon destructans

The occurrence of constitutive and induced antifungal compounds in primary roots of Pinus sylvestris seedlings was investigated, and total soluble phenols and lignification estimated, following challenge with the root pathogen Cylindrocarpon destructans. No reliably detectable phytoalexins were found, but the mean content of constitutive, antifungal diterpenic resin acids of the abietic acid group increased in the roots following infection. No diffuse lignitication was detected, but the content of cell-wall-bound phenolics increased with a concurrent decrease in the content of soluble phenols, although these changes were not statistically significant. The inhibitory effect of a commercial preparation of abietic acid on the germination of C. destructans spores was evaluated, and the significance of this class of compounds to defence in Scots pine seedlings is discussed.     

Response of sunflower and soybean to infection with Sclerotinia sclerotiorum with addition of organic amendments

Journal of Plant Diseases and Protection - The addition of compost, green waste biochar, and wood biochar to a pathosystem consisting of Sclerotinia sclerotiorum (Lib.) de Bary and two susceptible...